Hybrid pressure control concept for a speed variable AC motor pump in aerospace application Engelhardt, Joerg Greißner, Carsten 2002 - TUHH Open Research - frei zugänglich
More efficient fluid power systems using variable displacement hydraulic motors Biedermann, Olaf Engelhardt, Joerg Geerling, Gerhard 1998 - TUHH Open Research - frei zugänglich